1. Field of the Invention
The subject application relates to a method and a device for the heat treatment of metal materials in an industrial furnace comprising a heating chamber having a treatment chamber and a quenching chamber utilizing protective gas and reaction gas.
2. Description of Related Art
In order to carry out the heat treatment of metal materials in industrial furnaces it is already known to utilize catalysts for heat treatment furnaces in order to accelerate the reaction kinetics by means of catalyst support.
Among others, DE 36 32 577 describes catalyst beds, DE 38 88 814 describes catalyst-like linings having mesh-like structures of furnaces, DE 40 05 710 describes fully metallic oxidation catalysts containing Ni, Mn, Cr, and Fe, and DE 44 16 469 describes a two-stage nitro-carburizing by means of Ni or Cu catalysts.
DE 691 33 356 also assumes according to expert knowledge the utilization of catalysts in heat treatment furnaces for gas carburizing methods.
The further improved technologies utilized a catalytic stirring device in furnace atmospheres according to DE 690 13 997; a catalyst part on the basis of nickel oxide in furnaces for the heat treatment according to DE 694 01 425, and a catalyst device being connected to a heat treatment system according to DE 299 08 528.
Upon further pursuing the development trend the following can be determined:
the heat treatment of metals in a carbonized atmosphere according to GB 1,069,531;
the treatment of the surfaces of materials in annealing furnaces having a catalyst lining made of Ni oxide according to U.S. Pat. No. 3,620,518, which is attached to the ceramic interior wall and which enlarges the available surface;
utilizing a furnace for the heat treatment of metal parts having a protective atmosphere in furnaces having catalytic walls made of Ni according to U.S. Pat. No. 4,294,436;
the catalytic oxidation utilizing carbon compounds in gas flows according to U.S. Pat. No. 5,645,808;
the material treatment supported by plasma according to US 2006/0081567, and according to JP 62199761; and
the heat treatment and carburizing processes in a furnace having catalysts of any type seem to be completed, which is verified by further examples of prior art.
In summary, methods and furnaces for gas carburizing, having fireproof linings, metal catalysts made of Ni, Cu, Mn, Cr, Fe, etc, and also platinum, catalytic layers on ceramic linings, mesh-like catalyst linings, and catalytic stirring devices, and/or surface enlargements of the catalytic lining are largely known.
All of said methods and devices limit the savings of protective gas, the reduction of heat energy loss, and a supply of e.g. C/natural gas for carburizing that is tailored to specific requirements, and adjusting the C potential in the protective gas and excluding any non-adjustable/undesirable reactions, said limitations having obtained only few advantages in the further embodiment of the catalysts in industrial furnaces with regard to the construction thereof.
According to this documented prior art, the operation of the heat treatment of metal materials under protective gas is categorized in practice in the same manner as the gas carburizing such that the heat treatment furnace is aerated utilizing a reducing protective gas. This protective gas is usually composed of carbon monoxide, hydrogen, water vapor, carbon dioxide, and nitrogen. The introduction of aeration occurs in the heating chamber. In general a cold treatment chamber, a so-called quenching chamber, is connected to said heating chamber. Both chambers are usually separated by a gas permeable door. The gas fed into the heating chamber therefore also reaches the cold treatment chamber. However, the protective gas is guided out of the same at a burnout point, is safely ignited by an ignition burner, and burned.
This process is a continuous rinsing process, which, however, is associated with consistently high gas losses at the burnout point of the cold treatment chamber. However, this type of continuous rinsing of the heat treatment furnace is currently necessary in order to rinse any undesired gases penetrating the furnace after opening the door, such as air, out from the furnace again, or to also be able to carry out quick C potential modifications (atmosphere change), and in order to maintain a quasi stationary balance within the heating chamber. Without continuous rinsing the concentrations of carbon dioxide, oxygen, and water vapor would constantly rise in the heating chamber as the products of carburizing reactions with the components, since the degeneration reactions are executed in a slower manner using fed natural gas, than the carburizing reactions. This would mean that the carbon level would continuously drop, although, for example, natural gas would have been fed as the reaction gas for enrichment. The carbon potential does not become controllable until said rinsing, e.g. a maintaining of constant gas concentrations with regard to CO and H2 is carried out.
The practical knowledge confirms the previously described disadvantages of current methods, according to which the permanently high gas loss by means of rinsing the furnace, the energy loss of the protective gas value, and also the loss of process heat through the open system occur.
Thus, a much higher carbon mass stream is lost during carburizing due to rinsing, than is even required in order to carburize the materials like components.